Dodge Neon / Neon SRT-4. Manual - part 274

(N) and Oxygen. The three-way catalyst is most effi-
cient in converting HC, CO and NOx at the stoichio-
metric air fuel ratio of 14.7:1.

The oxygen content in a catalyst is important for

efficient conversion of exhaust gases. When a high
oxygen content (lean) air/fuel ratio is present for an
extended period, oxygen content in a catalyst can
reach a maximum. When a rich air/fuel ratio is
present for an extended period, the oxygen content in
the catalyst can become totally depleted. When this

occurs, the catalyst fails to convert the gases. This is
known as catalyst

9punch through.9

Catalyst operation is dependent on its ability to

store and release the oxygen needed to complete the
emissions-reducing chemical reactions. As a catalyst
deteriorates, its ability to store oxygen is reduced.
Since the catalyst’s ability to store oxygen is some-
what related to proper operation, oxygen storage can
be used as an indicator of catalyst performance.
Refer to the appropriate Diagnostic Information for
diagnosis of a catalyst related Diagnostic Trouble
Code (DTC).

The combustion reaction caused by the catalyst

releases additional heat in the exhaust system, caus-
ing temperature increases in the area of the reactor
under severe operating conditions. Such conditions
can exist when the engine misfires or otherwise does
not operate at peak efficiency. Do not remove spark
plug wires from plugs or by any other means short
out cylinders. Failure of the catalytic converter can
occur

due

temperature

increases

caused

unburned fuel passing through the converter. This
deterioration of the catalyst core can result in exces-
sively high emission levels, noise complaints, and
exhaust restrictions.

Unleaded gasoline must be used to avoid ruining

the catalyst core. Do not allow engine to operate
above 1200 RPM in neutral for extended periods over
5 minutes. This condition may result in excessive
exhaust system/floor pan temperatures because of no
air movement under the vehicle.

The flex joint allows flexing as the engine moves,

preventing breakage that could occur from the back-
and-forth motion of a transverse mounted engine.

Fig. 4 Catalytic Converter - LEV

1 - FLEX JOINT
2 - OXYGEN SENSOR - DOWNSTREAM

Fig. 5 Catalytic Converter - High Output Engine

1 - FLEX JOINT
2 - OXYGEN SENSOR - UPSTREAM
3 - OXYGEN SENSOR - DOWNSTREAM

Fig. 6 Flex Joint

11 - 22

EXHAUST SYSTEM

PL/SRT-4

CATALYTIC CONVERTER (Continued)

CAUTION: Due to exterior physical similarities of
some catalytic converters with pipe assemblies,
extreme care should be taken with replacement
parts.

There

are

internal

converter

differences

required in some parts of the country (particularly
vehicles

built

for

States

with

strict

emission

requirements) and between model years.

REMOVAL

WARNING: THE NORMAL OPERATING TEMPERA-
TURE OF THE EXHAUST SYSTEM IS VERY HIGH.
THEREFORE, NEVER ATTEMPT TO SERVICE ANY
PART OF THE EXHAUST SYSTEM UNTIL IT IS
COOLED. SPECIAL CARE SHOULD BE TAKEN
WHEN WORKING NEAR THE CATALYTIC CON-
VERTER. THE TEMPERATURE OF THE CONVERTER
RISES TO A HIGH LEVEL AFTER A SHORT PERIOD
OF ENGINE OPERATION TIME.

(1) Remove muffler and exhaust pipe. (Refer to 11

- EXHAUST SYSTEM/MUFFLER - REMOVAL)

(2) Disconnect the downstream oxygen sensor elec-

trical connector. (Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/O2 SENSOR - REMOVAL)

(3) Remove the exhaust manifold support bracket

(LEV only) (Fig. 7).

(4) Remove catalytic converter to exhaust manifold

attaching fasteners and remove converter from vehi-
cle (Fig. 8).

(5)

Remove and discard the flange gasket.

NOTE: When replacement is required on any com-
ponent of the exhaust system, original equipment
parts (or equivalent) must be used.

INSPECTION

Check catalytic converter for a flow restriction.

(Refer to 11 - EXHAUST SYSTEM - DIAGNOSIS
AND TESTING) Exhaust System Restriction Check
for procedure.

Visually inspect the catalytic converter element by

using a borescope or equivalent. Remove oxygen sen-
sor(s) and insert borescope. If borescope is not avail-
able, remove converter and inspect element using a
flashlight. Inspect element for cracked or melted sub-
strate.

NOTE: Before replacing a catalytic converter, deter-
mine the root cause of failure. Most catalytic con-
verter failures are caused by air, fuel or ignition
problems. (Refer to Appropriate Diagnostic Informa-
tion) for test procedures.

INSTALLATION

NOTE: When assembling exhaust system do not
tighten clamps until all components are aligned and
clearances are checked.

(1) Assemble catalytic converter to exhaust mani-

fold connection. Use a new flange gasket.

Fig. 7 Exhaust Manifold Support Bracket - LEV

1 - BRACKET
2 - BOLT (M10) - 54 N·m (40 ft. lbs.)
3 - BOLT (M12) - 95 N·m (70 ft. lbs.)
4 - NUT - 28 N·m (250 in. lbs.)

Fig. 8 Catalytic Converter to Exhaust Manifold

Connection - Typical

1 - PRESSED-IN STUDS
2 - NUTS
3 - GASKET

PL/SRT-4

EXHAUST SYSTEM

11 - 23

CATALYTIC CONVERTER (Continued)

(2) Install exhaust manifold support bracket (LEV

only). Tighten M10 bolt to 54 N·m (40 ft. lbs.), M12
bolt to 95 N·m (70 ft. lbs.), and nut to 28 N·m (250
in. lbs.).

(3) Install bolt attaching manifold support bracket

to the heat shield (NLEV only). Tighten bolt to 28
N·m (250 in. lbs.).

(4) Assemble muffler and exhaust pipe to catalytic

converter. Install muffler and pipe support isolators
to the underbody.

(5) Tighten the catalytic converter to exhaust man-

ifold fasteners to 28 N·m (250 in. lbs.) (Fig. 8).

(6) Working from the front of the system; align

each component to maintain position and proper
clearance with under body components. Tighten all
slip joint band clamps to 47 N·m (35 ft. lbs.).

CAUTION: Exhaust band clamps should never be
tightened such that the two sides of the clamps are
bottomed out against the center hourglass shaped
center block. Once this occurs, the clamp has lost
clamping force and must be replaced.

(7) If removed, install downstream oxygen sensor

(Refer to 14 - FUEL SYSTEM/FUEL INJECTION/O2
SENSOR - INSTALLATION).

(8) Connect downstream oxygen sensor electrical

connector.

(9) Start the engine and inspect for exhaust leaks.

Repair exhaust leaks as necessary.

(10) Check the exhaust system for contact with the

body panels. Make the necessary ajustments, if
needed.

HEAT SHIELDS

DESCRIPTION

The heat shields (Fig. 9), (Fig. 10) and (Fig. 11) are

needed to protect both the vehicle and the environ-
ment from the high temperatures developed in the
vicinity of the catalytic converter.

CAUTION: Avoid application of rust prevention com-
pounds or undercoating materials to exhaust sys-
tem floor pan heat shield on cars if equipped. Light
over-spray near the edges is permitted. Application
of coating will greatly reduce the efficiency of the
heat shields resulting in excessive floor pan tem-
peratures and objectionable fumes.

REMOVAL

(1) Raise vehicle on hoist.
(2) Remove fasteners attaching heat shield to

under body (Fig. 9), or engine component (Fig. 10)
(Fig. 11).

(3) Remove heat shield(s).

REMOVAL

(1) Using a flat scraper or sharp tool, locate an

edge of heat shield between the body and the heat
shield

(2) Attach pliers or locking pliers to the edge and

exert a pulling force while applying a heat gun to the
heat shield.

(3) Remove and clean heat shiel area with Mopar

Adhesive Cleaner.

INSTALLATION

(1) Position heat shield to underbody (Fig. 9) or

engine component (Fig. 10) (Fig. 11).

(2) Install and tighten heat shield fasteners (Fig.

9), (Fig. 10), or (Fig. 11)

(3) Inspect heat shield to exhaust system clear-

ances and adjust as necessary. (Refer to 11 -
EXHAUST SYSTEM - SPECIFICATIONS)

(4) Lower the vehicle.

(5) Start the engine and inspect for exhaust leaks.

Repair exhaust leaks as necessary.

(6) Check the exhaust system for contact with the

body panels. Make the necessary adjustments, if
needed.

Fig. 9 Heat Shield - Catalytic Converter

1 - NUT
2 - NUT
3 - HEAT SHIELD

11 - 24

EXHAUST SYSTEM

PL/SRT-4

CATALYTIC CONVERTER (Continued)

INSTALLATION

(1) Remove old adhesive and clean heat shield

aera with Mopar

t Adhesive Cleaner.

(2) Apply new heat shield to dry surface.

INTERMEDIATE PIPE

REMOVAL

WARNING: THE NORMAL OPERATING TEMPERA-
TURE OF THE EXHAUST SYSTEM IS VERY HIGH.
THEREFORE, NEVER WORK AROUND OR ATTEMPT
TO SERVICE ANY PART OF THE EXHAUST SYSTEM
UNTIL IT IS COOLED. SPECIAL CARE SHOULD BE
TAKEN WHEN WORKING NEAR THE CATALYTIC
CONVERTER. THE TEMPERATURE OF THE CON-

VERTER RISES TO A HIGH LEVEL AFTER A SHORT
PERIOD OF ENGINE OPERATING TIME.

(1) Raise vehicle on hoist and apply penetrating oil

to band clamp fastener of component being removed.

NOTE: Do not use petroleum-based lubricants when
removing/installing muffler or exhaust pipe isola-
tors as it may compromise the life of the part. A
suitable substitute is a mixture of liquid dish soap
and water.

(2) Remove the muffler. (Refer to 11 - EXHAUST

SYSTEM/MUFFLER - REMOVAL)

(3) Loosen band clamp at the catalytic converter to

intermediate pipe joint (Fig. 12)

(4) Remove intermediate pipe support isolator.

Separate at slip joint and remove intermediate pipe
(Fig. 12).

(5) Clean ends of pipes and muffler to assure mat-

ing of all parts. Discard broken or worn isolators,
rusted or overused clamps, supports, and attaching
parts.

NOTE: When replacement is required on any com-
ponent of the exhaust system, you must use origi-
nal equipment parts (or their equivalent).

INSTALLATION

When assembling exhaust system do not tighten

clamps until components are aligned and clearances
are checked.

(1) Assemble intermediate pipe to catalytic con-

verter and the isolator support to the underbody (Fig.
12).

(2) Install the muffler to intermediate pipe and the

isolator supports to the underbody.

(3) Working from the front of system; align each

component to maintain position and proper clearance
with underbody parts. (Refer to 11 - EXHAUST SYS-
TEM - ADJUSTMENTS)

(4) Tighten all band clamps to 47 N·m (35 ft. lbs.)

(Fig. 13).

CAUTION: Band clamps should never be tightened
such that the two sides of the clamps are bottomed
out against the center hourglass shaped center
block. Once this occurs, the clamp band has been
stretched and has lost its clamping force and must
be replaced.*

NOTE: *To replace the band clamp; remove the nut
and peel back the ends of the clamp until spot weld
breaks.

Fig. 10 Heat Shield - Engine Wire Harness

1 - HEAT SHIELD
2 - NUT - 11 N·m (100 in. lbs.)

Fig. 11 Heat Shield - Engine Wire Harness

1 - STUD
2 - HEAT SHIELD - WIRING
3 - NUT - 11 N·m (100 in. lbs.)
4 - BOLT - 28 N·m (250 in. lbs.)

PL/SRT-4

EXHAUST SYSTEM

11 - 25

HEAT SHIELDS (Continued)

Content .. 272 273 274 275 ..